The present invention relates to a semiconductor device to control the forward or reverse rotation of electrical equipment such as a motor.
A motor capable of forward rotation and reverse rotation is used in order to operate a power window or a door lock of an automobile for example. A mechanical switch (relay switch) is generally used for controlling the forward or reverse rotation of a motor. In recent years however, a forward reverse control circuit using a semiconductor device has been used increasingly.
FIG. 1 shows an example of an H-bridge circuit for materializing forward reverse control with a semiconductor device. A first arm is formed by coupling a drain of a MOS transistor 104 that is a P-channel MOS transistor of a high side to a drain of a MOS transistor 106 that is an N-channel MOS transistor of a low side. Meanwhile, a second arm is formed by coupling a drain of a MOS transistor 105 that is a P-channel MOS transistor of a high side to a drain of a MOS transistor 107 that is an N-channel MOS transistor of a low side. An H-bridge in which the first arm and the second arm are parallelly-coupled is formed by coupling sources of the high side MOS transistors 104 and 105 to a supply terminal 103 and coupling sources of the low side MOS transistors 106 and 107 to an earth terminal 102. A pair of terminals for driving a motor 108 is formed at a middle point node of the first arm and a middle point node of the second arm.
When the motor 108 rotates forward, a control circuit turns on the MOS transistors 104 and 107 and turns off the MOS transistors 105 and 106. As a result, electric current flows through the MOS transistor 104, the motor 108, the MOS transistor 107, and then the earth terminal 102 in sequence and the motor rotates forward. When the motor rotates reversely, the control circuit turns on the MOS transistors 105 and 106 and turns off the MOS transistors 104 and 107. As a result, electric current flows through the MOS transistor 105, the motor 108, the MOS transistor 106, and then the earth terminal 102 in sequence. On this occasion, the electric current flows in the motor 108 in a direction opposite to the direction of the flow in the event of forward rotation and hence the motor 108 rotates reversely.
An example of a semiconductor device for driving a motor is described in Japanese Unexamined Patent Application Publication No. 2007-12857.